Mirai Kaname's father is Lucifer, ruler of the demon world Makai. Imprisoned by the usurper Azazel prior to Devil Children Red Book's events, his disappearance spurred Mirai's journey into the Expanse to uncover her lineage.

Azazel impersonated Lucifer as the false Demon King in Central Land, manipulating Mirai into pursuing Setsuna Kai while concealing her true parentage. Mirai later learned Lucifer's identity from Mammon, a family acquaintance, and her mother's ghost in Sand Land. After Mirai and her half-brother Setsuna confronted and defeated Azazel in the Dark Palace, they freed Lucifer from magical chains. Upon release, Lucifer acknowledged both as his children and revealed his creation of the "Ragnarok" program – a system designed to break the world's cyclical fate by infusing demonic energy into human and demon realms. He transferred the choice of activating it to Mirai, refusing to impose his will.

In Devil Children Light & Dark, Lucifer faced assassination by Shin, a rebellion member manipulated by Drail. Jin, the protagonist, prevented this through time travel, altering that timeline. Lucifer reappeared in Messiah Riser, where the Imperium faction sacrificed him to absorb his power. His soul's resilience preserved Central Makai until protagonists Jin and Akira arrived. Following Gaap and Beelzebus's defeat, Lucifer was resurrected alongside other consumed demons.

As the overarching guide across multiple games, Lucifer's voice manifested in Setsuna and Mirai's dreams, instructing them to gather Messiah Horns and Eyes to forge the Keys of Norn. This granted access to the Oracle Room, where the fate of the worlds was decided. His character consistently emphasized free will, entrusting pivotal decisions to his children or allies rather than enforcing his authority as ruler.